(1) Field of the Invention
This invention relates to a substrate treating method and apparatus for performing a predetermined treatment on semiconductor wafers or glass substrates for liquid crystal displays (hereinafter simply called). More particularly, the invention relates to a technique for treating substrates coated with a film includes a high dielectric material such as oxidation hafnium oxide or zirconium oxide.
(2) Description of the Related Art
In the semiconductor field of recent years, multifunctional LSIs have been developed with an increasingly refined structure of devices such as transistors. While the operating speed of circuits has increased, the thinning of gate insulating oxide film is reaching the limit. That is, an increase of leak current occurring with the thinning of film poses a serious problem.
To solve this problem, oxide film used heretofore as the gate insulating film may be replaced by a high dielectric material which is attracting attention as a new material of high dielectric constant capable of suppressing leak current.
Such conventional construction has the following drawbacks.
High dielectric-constant materials that can be used in the semiconductor field include metal oxides such as aluminum and hafnium oxides. However, these oxides cannot be treated with an etching or cleaning solution used conventionally. Thus, although a high dielectric-constant material likely to replace the conventional material is under study, little progress has been made in its use.
In a semiconductor device, for example, it is considered essential to use a high dielectric material such as hafnium oxide or zirconium oxide for the gate insulating film in order to thin the gate insulating film for downsizing of the chip. High dielectric materials are chemically stable. Thus, when a thin film formed of a high dielectric material, e.g. hafnium oxide, is etched, hydrofluoric acid (fluoric acid) is used as an etching solution, and the substrate having a thin film of hafnium oxide formed thereon is immersed in fluoric acid for treatment.
However, fluoric acid cannot selectively etch only hafnium oxide, but will etch polysilicon or silicon oxide along with hafnium oxide.